Electrospun nanofibers have been applied in electrochemical sensors for the detection of various compounds, including metal ions, biomedically relevant molecules, and microorganisms.
4.1. Sensing of Glucose
One of the most popular sensors is a glucometer which monitors the level of glucose in body fluids. Several glucose sensors have been developed with the use of nanofibers. For example, Sapountzi et al. used a two-step approach-electrospinning and vapour phase polymerization-to produce core-shell nanofibers of PAN and Fe(III) p-toluenesulfonate hexahydrate (FeTos) coated with polypyrrole (PPy), using a mixture of pyrrole (Py) and pyrrole-3-carboxylic acid (Py3COOH) (1:2) as monomers [
37]. Electrospun PAN NFs were deposited directly on a gold electrode and exhibited the average diameter of 677 ± 20 nm. They were impregnated with FeTos, annealed at 70 °C, and coated with a conductive layer of polypyrrole, creating PAN/PPy/PPy3COOH NFs. After this process, an enzyme (glucose oxidase, GOx) was covalently immobilized on the modified electrodes through a reaction with EDC and NHS. The electrode was characterized and tested for glucose detection using EIS method. The biosensor achieved linearity in a wide range of glucose concentrations (20 nM–2 μM), low LOD (2 nM), as well as good stability and selectivity (tested towards ascorbic and uric acids).
Another group used a carbon nanofiber membrane decorated with NiMoO
4 NPs for enzymeless glucose detection [
38]. NFs were electrospun from a 10 wt% PAN solution in N,N-dimethylformamide (DMF) (average diameter 500 nm), stabilized, carbonized (average diameter 300 nm), and pretreated with a mixture of sulfuric and nitric acids, resulting in a carboxylated CNF membrane, on which NiMoO
4 NPs were synthesized. The morphology and electrochemical properties of obtained membrane were characterized. Sensing ability of the NiMoO
4/CNF was tested with CV technique, using a conventional three-electrode system (CNFs as a working electrode, Ag|AgCl as a reference electrode, and a Pt wire as an auxiliary electrode), and EIS. The results showed linearity in a wide concentration range (0.0003–4.5 mM), low LOD (50 nM), and good selectivity. In real sample analysis, the sensor exhibited a good recovery of 97.5–103.2% and the performance comparable to the results obtained by a commercial glucometer.
An electrochemical biosensor for the detection of glucose using graphene oxide (GO) nanofibers, gold nanoparticles (AuNPs), and copper nanoflowers was designed by Baek et al. [
39]. Poly(vinyl alcohol) (PVA) and GO served as the electrospinning solution to obtain nanofibers with the average diameter of 168 nm directly on a gold chip, which were later decorated with AuNPs. Then copper nanoflowers with immobilized enzymes-GOx and horseradish peroxidase (HRP)-were deposited on modified NFs. The whole structure was bonded to the gold chip with Nafion as a binding agent. The presence of AuNPs improved the conductivity, sensitivity, thermal resistance, mechanical and electrical properties of the sensor. The sensor and its components were characterized with various imaging techniques (e.g., TEM, FT-IR), and the detection capabilities were tested using chronoamperometry and CV with a conventional three-electrode cell (Ag|AgCl and Pt as reference and counter electrodes, respectively). Under optimized conditions, the sensor exhibited a wide linear range of 0.001–0.1 mM and the LOD of 0.018 μM.
Ni/CoO loaded carbon nanofibers were developed by Mei group using anionic surfactant-assisted equilibrium adsorption method and electrospinning [
40]. PAN was added to Ni/Co and sodium dodecyl sulfate solution and after stirring the solution was electrospun. Obtained NFs were then per-oxidized and carbonized. For electrochemical measurements, a glassy carbon electrode (GCE) modified with prepared NFs and CV technique were used. The sensor was tested for glucose determination at different concentrations, resulting in a linear range of 0.25–600 μM and LOD of 0.03 μM. Interference, stability, and real sample studies proved good selectivity and stability of constructed device.
Fu et al. presented a non-enzymatic glucose sensor with a glassy carbon electrode modified with Ni-Co layered double hydroxide-coated CNFs (CNF@Ni-Co LDH) [
41]. Pure carbon nanofibers with diameters in the range of 300–500 nm were obtained by electrospinning of PAN solution and annealing at 1000 °C. Then, chemical deposition was used to functionalize the NFs with Ni-Co LDH, resulting in a uniform flake-like structure on the surface of nanofibers. Finally, a GCE was modified with obtained nanocomposite. After the characterization of the material, its sensing performance towards glucose was tested with CV technique. Prepared sensor exhibited a low detection limit of 0.03 μM, a linear range of 1–2000 μM, and high sensitivity, good selectivity, reproducibility, and recovery.
In a different study, nickel cobalt sulfide-modified electrospun graphitic nanofiber film (EGF) was used for non-enzymatic glucose biosensing [
42]. Electrospinning of PAN solution and carbonization at 2000 °C were used to prepare graphite NFs. NiCo
2S
4 in a form of nanowire arrays were grown on graphite NFs by a two-pot hydrothermal reaction: hydrothermal synthesis of NiCo
2O
4 nanowires and chemical sulfidation (
Figure 7). The composite was used to modify a GCE. CV was applied for electrochemical measurements. The LOD of 0.167 μM and a wide linear range of 0.0005–3.571 mM were obtained. In addition, the sensor presented good sensitivity and selectivity, stability, and excellent reproducibility.
Adabi and Adabi also developed a non-enzymatic glucose sensor with the use of nickel-carbon NFs [
43]. CNFs were prepared from PAN solution via electrospinning, stabilization, and carbonization. Electrodeposition was used to place nickel particles on the surface of CNFs. Obtained nanofibers were characterized and used as a working electrode for glucose sensing, with Ag|AgCl reference electrode and Pt wire as an auxiliary electrode. The average diameter of CNFs was equal to 85.3 nm, which was a reduced result compared to the initial PAN NFs (124.4 nm). The presence of Ni on CNFs was confirmed by SEM, EDS, and XRD. The results of the electrochemical measurements presented the LOD of 0.57 μM, a linear range of 2 μM–5 mM, good selectivity and stability, as well as short response time (2 s). The sensor was also tested on real samples, proving to be promising for the detection of glucose in clinical applications.
Carbohydrate polymers can serve as a base for the nanofibers. Yezer and Demirkol blended cellulose acetate (CA) with chitosan (CS) to obtain electrospun NFs [
44]. After optimization, smooth NFs were collected directly on the GCE. Depending on the CA concentration, diameters of the NFs varied between 40 and 355 nm. After drying, glucose oxidase was immobilized on the modified electrode with glutaraldehyde as a cross-linking agent. The enzyme activity was tested, and the electrode was characterized electrochemically using CV, DPV, and EIS. Performed experiments revealed the detection limit of 4.8 μM and the linear range of 5.0 μM–0.75 mM. Tested interfering agents did not affect the performance of the sensor. Real sample analysis was also carried out, showing recovery between 96.5% and 103.0% (depending on the type of tested sample: artificial tears, urine, sweat, and serum).
Mehdizadeh et al. also used chitosan to prepare glucose sensor-CS/GO nanofibers, with the enzyme trapped between two NFs layers, which were used to modify a GCE [
45]. The NFs were electrospun directly on the electrode surface. The average diameter was between 105.11 and 386.49 nm, depending on the GO concentration. Then, the enzyme was immobilized on the nanofibers and after drying, another layer of NFs was deposited on the first layer to ensure that the enzyme stayed on the NFs (
Figure 8). Obtained nanostructures were analyzed using, i.a., microscopy, XRD, and FT-IR. Electrochemical studies were performed using CV with a conventional three-electrode system (modified GCE, Ag|AgCl and a Pt wire served as working, reference, and counter electrodes, respectively). The sensor presented linearity in a range of 0.05–20 mM, good selectivity and stability, and the detection limit was found at 0.02 mM.
Another glucose biosensor based on GOx and NFs was designed by Temoçin [
46]. An H
2O
2-sensitive GCE was modified with electrospun poly(ethyleneimine) (PEI)/PVA NFs (diameter 350–500 nm). The enzyme was immobilized on the surface of GCE with glutaraldehyde. UV-vis and electrochemical measurements were performed on the obtained electrode, and the NFs were characterized by SEM and FT-IR. The LOD of the biosensor, found based on DPV measurements, was 0.3 mM and a linear range was found at 2–8 mM and 10–30 mM. Additional tests confirmed the selectivity and stability of the sensor, and real sample analysis was performed with satisfying results.
Nanofiber-based sensor systems for the detection of glucose are summarized in
Table 1.
4.2. Sensing of Biomedically Relevant Molecules and Drugs
Electrochemical sensors based on nanofibers were developed towards various biomolecules and drugs, for instance, neurotransmitters, hormones, enzymes, and antibiotics.
Ratlam et al. presented a biosensor based on polyaniline (PANi)/carbon QDs composite (CQDs) for the detection of a neurotransmitter-dopamine [
49]. Electrospinning technique was used to obtain a nanofibrous matrix with the average diameter of NFs equal to 320 nm, and various techniques were used for its characterization, including SEM and FT-IR. For the electrochemical measurements, CV was applied, using a conventional three-electrode system, with NFs on fluorine doped tin oxide-coated glass substrate as a working electrode, Ag|AgCl as a reference electrode and a Pt wire as a counter electrode. The biosensor exhibited a low LOD of 0.1013 μM and a linear range of 10–90 μM, as well as good sensitivity and selectivity.
Ozoemena et al. used onion-like carbon and its carbon nanofiber composite (OLC-CNF) for dopamine detection [
50]. PAN and OLC served as precursors for electrospinning, and obtained NFs were later stabilized and carbonized, resulting in OLC-CNF (diameter of NFs 475–800 nm). The nanostructure was characterized and used to modify GCE, which served as a working electrode, alongside Ag|AgCl and Pt as reference and counter electrodes, respectively. The electrochemical characterization was based on CV, EIS, and square wave voltammetry. These tests allowed to find the LOD at 1.42 μM. Further examination showed selectivity, sensitivity, and applicability in real samples (tested for dopamine detection in its pharmaceutical formulation).
Nathani and Sharma presented a biosensing performance of mesoporous poly(styrene-block-methyl-methacrylate) (PS-b-PMMA) nanofibers towards streptavidin as a model analyte [
51]. The authors also explored how the sensing ability was influenced by the porosity of NFs. The block copolymer was electrospun into NFs with the average diameter of 336 ± 73 nm, which were later used to functionalize GCE. The NFs were further functionalized with biotin-hydrazine solution via EDC/NHS linking and blocked with bovine serum albumin (BSA). CV and DPV methods were used for electrochemical studies. The results indicated selectivity of the sensor, with the LOD for streptavidin at 0.37 fg/mL and a wide detection range of 10 fg/mL–10 ng/mL.
The use of cellulose acetate NFs allowed the detection of 25-hydroxy vitamin D
3 [
52]. CA NFs were electrospun onto a conducting paper substrate, which served as an electrode. NFs characterization showed the average diameter of 330 ± 3.5 nm. For vitamin D
3 detection, a specific monoclonal antibody was immobilized and blocked on the electrode and a chronoamperometric study was conducted. Obtained immunosensor showed selectivity and sensitivity, a wide linear range of 10–100 ng/mL, and a low LOD of 10 ng/mL. The results were validated using ELISA technique of serum samples.
Hybrid nanofibers composed of cellulose monoacetate and Nafion (CMA/N) were used in a DNA biosensor [
53]. The CMA/N blend was electrospun, resulting in NFs with the average diameter between 500 nm and 1.5 μm, which were analyzed using methods such as SEM and FT-IR. The sensing performance was focused on the oxidation of guanine of immobilized DNA. Pencil graphite electrodes were functionalized with NFs and single strand DNA probes, unmodified and NH-modified. DPV measurements were performed in a three-electrode system, with Ag|AgCl and a Pt wire as reference and counter electrodes, respectively. The oxidation signals were compared for both types of DNA and NFs with different CMA to Nafion ratio, reaching maximum for pure CMA NFs and unmodified DNA.
Wang et al. synthesized MoS
2 nanosheet arrays/carbon nanofibers (MoS
2 NSA/CNF) and employed them in a sensor for simultaneous detection of levodopa, a dopamine precursor, and uric acid [
54]. The composite was obtained using electrospinning of PAN to synthesize CNFs with the average diameter of 200 nm, and hydrothermal synthesis to grow NSA on the surface of NFs, and it was characterized with SEM and XRD. For the electrochemical measurements, CV and DPV methods were used. The results showed the LOD of 1 μM and a linear range of 1–60 μM for both analytes, as well as good sensitivity, selectivity, reproducibility, and stability of the electrode.
In another work, honey/PVA core-shell nanofibers, multi-walled carbon nanotubes (MWCNTs), and AuNPs, as well as an aptamer, were used to modify a GCE for the impedimetric determination of MUC1, a breast cancer marker [
55]. Co-axial electrospinning was used to obtain NFs, collected directly on the electrode, with the average diameter of 100 ± 15 nm. Then, the electrode was functionalized with AuNPs and MWCNTs. The aptamer was immobilized after activating the carboxylic groups of the nanotubes via EDC/NHS reaction. SEM and FT-IR were used to characterize obtained material, and the electrochemical measurements were carried out using EIS and CV methods. The sensor showed a wide linear range of 5–115 nM and the detection limit equal to 2.7 nM. Further tests revealed good stability, sensitivity, and selectivity, and satisfactory real sample analysis results.
Nanofibers modified with AuNPs and MWCNTs for breast cancer biomarker determination was also investigated by Adabi et al. [
56]. In this study, CNF mat functionalized with AuNPs, cysteamine, MWCNTs, and antibody, was used for the detection of human epidermal growth factor receptor 2 (Her-2). The characterization of obtained electrode was based on field emission SEM (FESEM) and EDS, and CV was adopted for the electrochemical performance examination. The immunosensor reached a low LOD of 0.45 ng/mL and a linear range of 5–80 ng/mL. Good reproducibility and repeatability were obtained. The performance of the sensor was confirmed by real sample analysis.
Nicotine was the target of a sensor based on MWCNT/CS NFs [
57]. Functionalized MWCNTs and chitosan blend was used for the electrospinning, resulting in NFs with the average diameter between 95.47 nm and 131.01 nm, depending on the MWCNTs percentage. Obtained nanostructure was collected directly on the GCE. Its characterization included FESEM, TEM, AFM, and FT-IR. For the electrochemical measurements, CV was used. The results showed a linear range between 0.1 and 100 μM and the detection limit of 30 nM. The sensor exhibited good selectivity, sensitivity, stability, and reproducibility.
The NiO-Au hybrid NFs were adopted in an aptasensor for the determination of progesterone (P4), a steroid hormone [
58]. The NFs were electrospun from a composite consisting of Ni(NO
3)
2, HAuCl
4, and polyvinylpyrrolidone (PVP), and were then functionalized with graphene QDs (GQDs). A screen printed carbon electrode was used as a working electrode after modification with GQDs-NiO-Au NFs and MWCNTs. The P4-specific aptamer was immobilized on the electrode via EDC/NHS reaction and blocked with BSA. For electrochemical experiments CV, EIS, and DPV techniques were used. The aptasensor showed great selectivity and stability, with the LOD of 1.86 pM and a linear range of 0.01–1000 nM.
Nanofiber-based sensor systems for the detection of biomolecules are summarized in
Table 2.
Several publications concerning NF-based sensors toward drugs have been reported. For example, Vafaye et al. presented a study of an AuNP/CNF aptasensor for the determination of penicillin in milk samples [
66]. CNFs were obtained by electrospinning from a PAN solution and carbonization. The electrodeposition was adopted to functionalize NFs mat with AuNPs. Lastly, a penicillin aptamer was immobilized on the surface of the nanostructure. SEM, EDS, and Raman spectroscopy were used for the characterization of the electrode, and the electrochemical measurements were conducted with the CV method, with Ag|AgCl as a reference electrode and a Pt wire as an auxiliary electrode. The results indicated good selectivity, stability, and reproducibility of the sensor, a wide linear range of 1–400 ng/mL, and the LOD was found at 0.6 ng/mL. The sensor was validated by comparison with HPLC results.
Modified CNFs were also used in a sensor for colchicine detection [
67]. The authors synthesized CuO NPs and added them to a PVA solution, which was later used for the fabrication of NFs through electrospinning. Obtained NFs were then stabilized and carbonized to give CuO/CNFs. A magnetic ionic liquid (MIL), 1-butyl-3-methylimidazolium tetrachloroferrate ([Bmim]FeCl
4) was also prepared. GCE was modified with both CuO/CNF and MIL, and Nafion was cast on the surface for binding. Obtained materials were characterized (e.g., SEM, FT-IR), and CV and DPV methods were used for electrochemical measurements. The average diameter of the spherical CuO NPs and CNFs was 48 nm and 80 nm, respectively. The linear range and the detection limit of the sensor were 1–100 nM and 0.25 nM, respectively. In addition, the sensor exhibited good sensitivity, selectivity, and stability and was used for real sample analysis with satisfactory results.
Acetaminophen (APAP) and p-hydroxyacetophenone (p-HAP) were simultaneously detected by a sensor utilizing a composite SnO
2-CNF [
68]. PAN mixed with SnCl
2·2H
2O served as a precursor for the NFs, which were later carbonized to obtain SnO
2-CNF with a diameter in the range of 400–500 nm. This material was used to modify a GCE. Microscopic and spectroscopic techniques were used for the characterization of the electrode, and EIS and DPV methods were adopted for electrochemical measurements. The sensor showed great reproducibility, repeatability, and stability, as well as high selectivity proven by the interference study. It was also successfully applied in real sample analysis. For APAP, the linear range was 0.5–700 μM with the LOD of 0.086 μM, while for the p-HAP these parameters were 0.2–50 μM and 0.033 μM, respectively.
Bahrami et al. developed a sensor based on magnetic nanofibers for the detection of morphine [
69]. The NFs were prepared from PVA and iron salt precursors via electrospinning and a thermal process and had diameters in a range of 70–120 nm. Graphite powder, paraffin oil, and NFs were used to obtain a modified carbon paste electrode (CPE). Electrochemical studies were performed using CV and DPV techniques. XRD, SEM, and FT-IR were used for the characterization of the electrode. The sensor exhibited good sensitivity and selectivity, with a detection limit of 1.9 nM and a wide linear range of 0.0033–245 μM.
Table 3 summarizes NFs-based sensors for the electrochemical detection of drugs.
An aptasensor for
Salmonella enterica serovar was developed by Fathi et al. [
73]. CNFs (average diameter 90 ± 10 nm) were fabricated from PAN precursor, mixed with CS, and deposited on a pencil graphite electrode. The surface of the electrode was further modified with AuNPs, an aptamer, and methylene blue (MB) (
Figure 9). The obtained sensor was electrochemically characterized by CV and EIS techniques. The LOD was found at 1.223 CFU/mL, and the sensor showed a wide linear range of 10–10
5 CFU/mL, good selectivity, reproducibility, and stability.
Liberato et al. presented an immunosensor for the detection of
Leischmania braziliensis, where the recognition was based on an interaction between an epitope designed from the antigen and its specific antibody [
74]. Polyamide 6 (PA6)/CS NFs were fabricated using the electrospinning technique (diameter in a range of 15–170 nm) and characterized with, i.a., SEM, XRD, and FT-IR. For electrochemical studies, CV and EIS were adopted. Cellulose acetate covered by a gold layer was used as a working electrode. The electrode was modified with NFs, promastigote surface antigen, and BSA. The results showed a low detection limit of 1.6 pg/mL and a linear range of 2.5–10 pg/mL (of specific antibodies). The sensor was also examined by real sample analysis that included both positive and negative serum samples.
In a different work, functionalized CNFs were used for the detection of
Pseudomonas aeruginosa [
75]. The authors prepared hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers (CNCNF) with a rosary-like structure. To do that, Fe
2O
3 nanocapsule templates were covered by a layer of polydopamine (which served as a carbon source), were later transformed into carbon N-doped nanocapsules and the iron oxide core was etched. NFs were fabricated from a PAN and nanocapsules solution via electrospinning and carbonization. Obtained CNCNF were used for the modification of a GCE. In order to immobilize the aptamer on the electrode surface, it was covered with a layer of mercaptopropionic acid, and EDC/NHS coupling was used to secure the biomolecule on the electrode. The electrochemical measurements were performed using CV and EIS methods. The sensor presented good stability, selectivity, repeatability, satisfactory results in real sample analysis, with a linear range of 10–10
7 CFU/mL and the LOD at 1 CFU/mL.
Electrospun CNFs were also applied in a sensor for a hepatitis B virus detection [
76]. CNFs were prepared from a PAN solution (diameter between 70–282 nm, depending on DMF/acetone ratio) and examined with SEM, XRD, and Raman spectroscopy, and served as the electrode. Electropolymerization was used to modify the CNF electrode with glutamic acid, to which a DNA fragment was attached via EDC/NHS reaction to fabricate a biosensor. CV was adopted for electrochemical measurements, which revealed a detection limit equal to 1.58 pM and a wide linear range of 1 pM–1 μM, as well as good selectivity and stability.
4.3. Sensing of Metal Ions
Electrospun NFs have also found application in the detection of metal ions. For example, Ehzari et al. constructed an aptasensor for Hg
2+ detection using CPE modified with polyethersulfone NFs, with the average diameter of 130 nm, and thiol-capped CdTe QDs [
77]. In this work, nanomaterials served as an amplifier for the signal generated by an interaction between mercury ions, thymine, and methylene blue. NFs-QDs nanocomposite was collected directly on the CPE during the electrospinning process. The surface of the electrode was activated with EDC/NHS to immobilize an aptamer, and it was subsequently immersed in MB. The sensor was then exposed to various Hg
2+ solutions, then immersed in MB again. Characterization of the sensor and its components was performed (e.g., SEM, FT-IR, EDX). The electrochemical sensing performance was examined with DPV. The results showed good specificity, stability, and repeatability of the sensor, with a wide linear range of 0.1–150 nM and the detection limit of 0.02 nM.
Another aptamer sensor for mercury ions detection was developed by Xie et al. [
78]. Carbon ionic liquid electrode was functionalized with platinum nanoparticles (PtNPs)/CNF and AuNPs. The NFs were fabricated from a PAN solution through electrospinning and carbonization and had the average diameter of 400 nm. Then, PtNPs were formed on the CNF. This composite was used to modify the electrode, and then AuNPs were synthesized on the surface and the aptamer was immobilized on the electrode. As in the previous example, the sensing mechanism was based on the Hg
2+-thymine binding. Electrochemical measurements were conducted using CV and EIS techniques, showing a wide linear range (1 fM–1 μM) and a low LOD of 0.33 fM. Selectivity, stability, and repeatability were also confirmed by the test, and real sample analysis gave satisfactory results.
A different approach to Hg
2+ detection was presented by Teodoro et al. [
79,
80]. They used a nanocomposite composed of PA6 NFs (average diameter of 130 ± 32 nm), on which carbon nanowhiskers and reduced GO hybrid material was adsorbed. After characterization, electrochemical measurements were performed, using DPV and CV techniques, in a conventional three-electrode system, with fluorine tin-oxide electrode modified with the obtained nanocomposite as a working electrode, Ag|AgCl as a reference electrode, and Pt as a counter electrode. The LOD and the linear range were found at 0.52 μM and 2.5–200 μM, respectively. An interference study confirmed selectivity, and the sensor was tested on real samples.
Liu and Zhang used nitrogen-doped CNF with metal-organic NPs for Cd
2+ and Pb
2+ ions detection [
81]. ZIF-8 NPs were prepared and added to PAN solution, from which NFs were electrospun and carbonized in a nitrogen atmosphere, resulting in nitrogen-doped CNFs. GCE modified with CNFs was used as a working electrode. For the electrochemical measurements, anodic stripping voltammetry and differential pulse anodic stripping voltammetry were used. The sensor showed a linear range of 2–100 μg/L and 1–100 μg/L, and the LOD of 1.11 μg/L and 0.72 μg/L for Cd
2+ and Pb
2+, respectively. The selectivity was confirmed by an interference study, and real sample examination showed acceptable results.
A Pb
2+ sensor was also presented by Oliveira et al. [
82]. This sensor was based on L-cysteine modified ZnO NFs (average diameter of 335 nm). The NFs were fabricated from a PVA-zinc acetate solution via electrospinning and annealing, and then functionalized with L-Cys. This composite was used to modify a GCE. The NFs and the electrode were characterized, i.a., with SEM and FT-IR. Electrochemical measurements were carried out using square wave anodic stripping voltammetry (SWASV). The results indicated good stability, selectivity, and repeatability, and the LOD and the linear range were 0.397 μg/L and 10–140 μg/L, respectively.
Modified CNFs were adopted for As
3+ determination [
83]. Fe-CNFs were prepared from a PAN and iron acetylacetonate solution, then polyaniline was polymerized on their surface and finally, the composite was decorated with AuNPs. The obtained material was used for a GCE modification. SEM, TEM, XRD, and X-ray photoelectron spectroscopy (XPS) techniques were used for the characterization, and CV and SWASV were used for the electrochemical analysis. Excellent sensitivity and selectivity were achieved, with a low LOD at 6.67 nM in a linear range of 0.07–5.34 μM.
Sensors for the detection of metal ions are summarized in
Table 4.